Remove redfish login and logout from lib code

With this change, the test script caller is expected to have the
valid session before invoking the changed keywords in library.

Changes:
      - Remove login/logout from lib/bmc_redfish_utils.robot
        for power and reset operation.
      - Update impacted test suites.

Tested: To identify the impact, ran the existing test bucket and
        the result is looking good.

Change-Id: I6df69d6fcc4c38470fdb2ec3b31fb28beb726d70
Signed-off-by: George Keishing <gkeishin@in.ibm.com>
diff --git a/lib/bmc_redfish_utils.robot b/lib/bmc_redfish_utils.robot
index 0fb2c50..5936574 100644
--- a/lib/bmc_redfish_utils.robot
+++ b/lib/bmc_redfish_utils.robot
@@ -31,11 +31,9 @@
     #  }
     # }
 
-    Redfish.Login
     ${target}=  redfish_utils.Get Target Actions  /redfish/v1/Systems/system/  ComputerSystem.Reset
     ${payload}=  Create Dictionary  ResetType=${reset_type}
     ${resp}=  Redfish.Post  ${target}  body=&{payload}
-    Redfish.Logout
 
 
 Redfish BMC Reset Operation
@@ -50,13 +48,9 @@
     #  "target": "/redfish/v1/Managers/bmc/Actions/Manager.Reset"
     # }
 
-    Redfish.Login
     ${target}=  redfish_utils.Get Target Actions  /redfish/v1/Managers/bmc/  Manager.Reset
     ${payload}=  Create Dictionary  ResetType=GracefulRestart
-    ${resp}=  Redfish.Post  ${target}  body=&{payload}
-    # The logout may very well fail because the system was just asked to
-    # reset itself.
-    Run Keyword And Ignore Error  Redfish.Logout
+    Redfish.Post  ${target}  body=&{payload}
 
 
 Reset BIOS Via Redfish